如何在numpy中将矩阵变成对角矩阵? [英] how to make matrix into diagonal matrix in numpy?

问题描述

给定矩阵:

x = matrix([[ 0.9,  0.14], [ 0.15,  0.8]])

如何将第一列x[:,0]变成numpy中的对角矩阵?得到:

how can you make the first column, x[:,0], into a diagonal matrix in numpy? to get:

matrix([[0.9, 0],
        [0, 0.15]])

推荐答案

numpy.diag( x.A[ :, 0 ] )

应该这样做.

matrix和array之间的区别在这里至关重要.仅numpy.diag( x[ :, 0 ] )不会获得相同的结果.当x是matrix时，x.A是numpy.asarray( x )的简写.

The difference between a matrix and an array is crucial here. You won't get the same result from just numpy.diag( x[ :, 0 ] ). x.A is a shorthand for numpy.asarray( x ) when x is a matrix.

因此，出于同样的原因，我想确切地回答您的问题，我想我不应该忘记将答案从array转换回matrix:

So by the same token, to answer your question precisely I guess I shouldn't forget convert the answer from an array back to a matrix:

numpy.matrix( numpy.diag( x.A[ :, 0 ] ) )

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